1. Field of the Invention
The present invention relates to a riveting die apparatus, and particularly to a riveting die apparatus with a positioning device.
2. Related Art
A conventional riveting die apparatus, as shown in FIG. 2, comprises an upper die 10 and a lower die 20. A guide post 11 depends from the upper die 10. A pair of punches 12 respectively depends from the upper die apparatus 10 on opposite sides of the guide post 11. Each punch 12 has a conical head 124. The punches 12 are shorter than the guide post 11. The lower die 20 comprises a lower mold plate 22, and a guide bushing 26. A pair of through holes 24 is defined in the plate 22, for respectively receiving the conical heads 124 of the punches 12.
In operation, a pair of stacked workpieces (not shown) is placed over one through hole 24. Holes (not shown) defined in the workpieces are aligned with the through hole 24. Similarly, another pair of similar stacked workpieces is placed over the other through hole 24 of the lower mold plate 22. The upper die 10 is moved downwardly. The guide post 11 is firstly received into the guide bushing 26, thereby guiding movement of the upper die 10. The conical heads 124 of the punches 12 then enter the holes of the workpieces. The conical heads 124 of the punches 12 then enter the through holes 24 of the lower mold plate 22. The two pairs of stacked workpieces on opposite sides of the lower mold plate 22 are thus respectively riveted together.
However, the die apparatus does not itself provide any means for correctly positioning the workpieces before the upper die 10 is moved downwardly. Workpieces are often not precisely positioned on the lower mold plate 22, particularly when the die apparatus operates continuously at high speed. Thus imperfect and damaged workpieces are frequently formed.
It is strongly desired to provide a die apparatus with a positioning device which overcomes the above problems encountered in the prior art.
Accordingly, an object of the present invention is to provide a riveting die apparatus with a positioning device which readily and precisely positions workpieces.
To achieve the above-mentioned object, a riveting die apparatus incorporating a positioning device in accordance with the present invention comprises an upper die and a lower die. The upper die comprises a pair of punches and a guide post between the punches. The lower die comprises a lower mold plate. The lower mold plate defines two through apertures corresponding to the punches, and two piston holes respectively in communication with the through apertures. Two blocks are secured below the lower mold plate. Each block defines a blind hole in communication with the corresponding piston hole of the lower mold plate. A spring is accommodated in each combined piston hole and blind hole. A rod is movably received in each through aperture. A base of each rod is accommodated in the piston hole, and abuts the corresponding spring. A guide bushing is mounted on the lower mold plate for guiding movement of the guide post. Workpieces placed on the lower mold plate are precisely positioned by the rods prior to operation of the die apparatus.